Garrick ( Peak Condition ), a sports medicine specialist, and writer Radetsky ( Pace Walking ) view exercise primarily as a means to better athletic performance. Their book therefore provides not a choice of fitness programs, but a wealth of information on how to utilize stretching, aerobics and strength training to improve physical conditioning before and in between tennis matches or bicycle trips. The authors describe and illustrate a range of exercises tailored to the needs of specific sports, problems and muscle groups, but the lack of an outline for a daily or weekly workout schedule makes this information useful to only highly motivated people capable of designing their own training programs. And while the section on overcoming past or minor injuries reminds us to seek professional advice, the book's suggestion that self-guided rehabilitation is sometimes fruitful seems potentially dangerous. For athletes already well-versed in careful training, however, the book could serve as a valuable resource. Author tour. (June)